Hearing Music That Is Not There
People with hearing loss can develop Musical Ear Syndrome, a condition where the brain creates vivid, phantom melodies. Because the brain craves sensory input, it starts hallucinating familiar songs when external sound is absent.
This phenomenon is the auditory version of phantom limb syndrome or visual hallucinations experienced by those with vision loss. When the ears stop sending enough data to the brain, the auditory cortex essentially turns up the gain and begins inventing its own soundtrack. These internal concerts can range from simple jingles to full orchestral pieces that sound startlingly real. It is a fascinating example of how our minds struggle to fill the void when our senses are deprived.
Source: Musical ear syndrome